I just had my windows done recently, and I just noticed the GPS text rarely comes on. 80% of the time it's off.

I called the shop and told them about it, and he gave me some answer about how Acuras don't have this problem and that he would have to talk to his tint manufacturer about it. When I first went in there he told me his tint was Solarguard, but the box was an off-brand.

I'm going down there tomorrow and he said he wanted to see it in action. We'll see.

Now that I think about it, my FM reception is a lot worse inside my parking garage at work too. Blah!

 

When I first had my my windows tinted with titanium tint?, my cell phone went haywire, getting no reception. About an hour later, it was fine, and up to this day, no problem
I also had a pioneer nav with the nav antenna in the rear window and it worked fine .

Mine wasn't too reflective, so I guess I was able to receive receptions and signals.
Sorry, no help to you